1. Field of the Invention
The present invention relates to an air conditioner, such as a gas engine heat pump, which uses hot water.
2. Description of the Related Art
A conventional air conditioner, which uses hot water, is shown in FIG. 5. In FIG. 5, reference number 1 denotes an engine, 2 denotes a compressor, 13 denotes an outer heat exchanger for heat exchanging between outside air and a refrigerant, 21 denotes a radiator for radiating heat of an engine cooling water, 51 denotes an engine cooling water circuit in which the engine cooling water circulates, and 52 denotes a refrigerant circuit in which the refrigerant circulates. According to this air conditioner, the radiator 21 is interposed between the outer heat exchangers 13 and 13; therefore, the refrigerant is vaporized using not only heat of the outside air but also the waste heat of the engine 1. Moreover, such structure is called xe2x80x9cradiator interposition structurexe2x80x9d below.
In this air conditioner, the waste heat is conducted through fins provided with the radiator and through the air, and then it is recovered. Therefore, a portion of the waste heat of the engine 1 is discharged into atmosphere, and the waste heat cannot be utilized efficiently. Due to this, the refrigerant is vaporized sufficiently in the outer heat exchanger 13 when the temperature of the outside air is low, and heating capability of the air conditioner is affected by the temperature of the outside air.
Another conventional air conditioner is shown in FIG. 6. In this air conditioner, the water heat exchanger 16 is connected in series to the outer heat exchanger 13 in the engine cooling circuit 51 and the refrigerant circuit 52. Thereby, the waste heat of the engine 1 can be recovered by the water heat exchanger 16, in addition to the radiator 21. Moreover, such structure is called xe2x80x9cwater heat exchanger series structurexe2x80x9d below. In this air conditioner, both the outer heat exchanger 13 and the water heat exchanger 16 resist the circulating refrigerant, and thereby the flow pressure loss of the refrigerant increases. Consequently, a large amount of refrigerant has to be contained in refrigerant circuit 52.
Moreover, in the radiator interposition structure shown in FIG. 5 and the water heat exchanger series structure shown in FIG. 6, in order to increase heat recovered to the refrigerant, it is necessary to drive a fan 53 (in FIG. 5, but not shown in FIG. 6) for introducing the outside air using a lot of force. Consequently, the problem arises that increased electric power is required for the fan 53 and the fan 53 generates noise.
Therefore, an object of the present invention is to provide an air conditioner which can efficiently vaporize the refrigerant using the waste heat of the engine; which has a stable heating capability regardless of the temperature of the outside air; and which can decrease the electric power required for the fan and thereby decrease the noise due to the fan, in a heating operation.
In order to achieve the object, the present invention provides an air conditioner comprising:
a refrigerant circuit comprising a compressor for compressing a refrigerant; an outer heat exchanger for exchanging heat between the refrigerant and outside air; a restrictor for restricting the refrigerant flowing out from a water heat exchanger; and an inner heat exchanger for exchanging heat between inside air and the refrigerant;
an engine cooling water circuit comprising an engine for driving the compressor; and a radiator for exchanging heat between engine cooling water and outside air; and
a water heat exchanger for exchanging heat between the refrigerant circulating in the refrigerant circuit and the engine cooling water circulating in the engine cooling water circuit;
wherein an evaporator comprising the outer heat exchanger and the water heat exchanger connected in parallel to the outer heat exchanger, is provided in the refrigerant circuit.
According to the air conditioner, the outer heat exchanger and the water heat exchanger which is connected in parallel to the outer heat exchanger is provided in the refrigerant circuit. Specifically, the outer heat exchanger and the water heat exchanger are connected in such a way that each operates whether the one is operating or not. Therefore, according to the air conditioner of the present invention, the resistance applied to the refrigerant and the flow pressure loss of the refrigerant can be reduced. Moreover, the heat of the engine cooling water is not discharged into the atmosphere in the water heat exchanger; therefore, the engine waste heat can be utilized efficiently to heat the refrigerant.
In the air conditioner, it is preferable to further comprise an adjusting device for adjusting the amount of the refrigerant supplied into the outer heat exchanger and the water heat exchanger, in response to the temperature of the outside air.
According to the air conditioner, when the temperature of the outside air is low, for example, when it is less than 2xc2x0 C., the operation of the outer heat exchanger is stopped by supplying no refrigerant into the outer heat exchanger, and thereby only the water heat exchanger is operated. The water heat exchanger utilizes the engine waste heat, and it can heat the refrigerant. Therefore, even when the temperature of the outside air is low, the refrigerant can be heated sufficiently, and a heating operation can be carried out without being affected by the temperature of the outside air. Furthermore, when the outer heat exchanger and the water heat exchanger using the engine cooling water at high temperature are operated together, the load applied to the outer heat exchanger can be reduced. Thereby, the electric power required for the fan for introducing the outside air can also be reduced; therefore, noise due to the fan can also be decreased.
In the air conditioner, it is preferable that the outer heat exchanger comprises a refrigerant pipe for falling and discharging a liquid refrigerant condensed therein, the outer heat exchanger is positioned separately from the radiator, and the refrigerant circuit further comprises a liquid refrigerant recovery pipe for flowing the liquid refrigerant discharged from the refrigerant pipe into the refrigerant circuit in which the refrigerant is flowing.
In particular, it is more preferable that the outer heat exchanger is positioned at upstream side with respect to the radiator in the flow direction of the outside air.
Moreover, it is more preferable that the refrigerant pipe is provided in the outer heat exchanger so that upstream portions are always lower than downstream portions in the flow direction of the refrigerant in the heating operation.
It is also more preferable that the refrigerant pipe provided in the outer heat exchanger comprises no sink portion.
Furthermore, it is the most preferable that the refrigerant pipe provided in the outer heat exchanger comprises a plurality of straight tube portions and a plurality of U-shaped tube portions; the straight tube portion extends so that upstream portions are always lower than downstream portions in the flow direction of the refrigerant in the heating operation; and the U-shaped tube portion is arranged between the straight tube portions so that upstream portions are always lower than downstream portions in the flow direction of the refrigerant in the heating operation.
According to the air conditioner, the radiated heat from the radiator does not reach to the outer heat exchanger. Due to this, a decrease of the cooling capability of the air conditioner can be prevented. In addition, according to the air conditioner, when the temperature of the outside air is low, the outer heat exchanger is not operated, and only the water heat exchanger is operated, the liquid refrigerant condensed in the outer heat exchanger can be fallen and discharged from the outer heat exchanger. The discharged liquid refrigerant flows through the refrigerant recovery pipe and reaches to the refrigerant circuit in which the refrigerant is circulating. Consequently, the refrigerant does not accumulate in the outer heat exchanger, and thereby a decrease of the- amount of the refrigerant circulating in the refrigerant circle can be prevented, when the temperature of the outside air is low.
In the air conditioner, it is preferable that refrigerant circuit further comprises an accumulator for accumulating a liquid refrigerant which is positioned lower than said outer heat exchanger, and the liquid refrigerant recovery pipe is connected to the accumulator.
According to the air conditioner, the liquid refrigerant which is discharged from the outer heat exchanger, flows through the refrigerant recovery pipe, and flows into the accumulator. The refrigerant recovered in the accumulator can flow in the refrigerant circuit again. Consequently, the refrigerant does not accumulate in the outer heat exchanger, and thereby a decrease of an amount of the refrigerant circulating in the refrigerant circle can be prevented.
In the air conditioner, it is preferable to further comprise a junction pipe, which connects to a refrigerant pipe extending from an exit of the outer heat exchanger and a refrigerant pipe extending from an exit of the water heat exchanger in heating operation, and which is positioned lower than the outer heat exchanger; and the refrigerant recovery pipe is connected to the junction pipe.
According to the air conditioner, the liquid refrigerant, which is fallen and discharged from the outer heat exchanger, flows through the refrigerant recovery pipe, is confluent with a gas refrigerant flowing out from the water heat exchanger, reaches into the refrigerant circuit in which the refrigerant is circulating. The refrigerant recovered in the accumulator can flow in the refrigerant circuit again, Consequently, the accumulation of the refrigerant in the outer heat exchanger can be prevented, and thereby a decrease of an amount of the refrigerant circulating in the refrigerant circle can also be prevented.
In the air conditioner, it is preferable that a constant pressure expansion valve is used as the restrictor.
When an electric expansion valve is used as the restrictor, in order to adjust the temperature of the refrigerant at the exit of the water heat exchanger in the flow direction of the refrigerant in the heating operation, it is necessary to check the pressure and the temperature of the refrigerant at the same time. In contrast, when the constant pressure expansion valve is used as the restrictor, it is not necessary to check the pressure of the refrigerant flowing out from the water heat exchanger 16 because the pressure is automatically adjusted, and it is only necessary to check its temperature. Consequently, the advantages can be obtained, that the reliability of the air conditioner can be improved, the constant pressure expansion valve itself is cheap, and an pressure sensor is not required; therefore, the cost of the air conditioner can be reduced.